Test handlers are used in the semiconductor industry for testing electronic devices (eg. light-emitting diodes (LEDs), integrated circuits (IC) packages and semiconductor chips) by one or more test stations. It is necessary to position the electronic devices in a desired orientation before subjecting the electronic devices to testing at one or more test stations.
A vibratory bowl feeder is typically used to transport electronic devices to a test handler for testing. The vibratory bowl feeder comprises a linear track, and the orientation of the electronic devices is determined by a sensor located along the linear track. As the electronic devices are being successively conveyed by vibratory motion towards a turret handler of the test handler, the electronic devices which are found to have the desired orientation are picked up by respective pick heads of the turret handler and indexed by the test handler to one or more test stations of the test handler. The electronic devices which are found not to have the desired orientation are removed from the linear track. These electronic devices will then have to wait to be re-conveyed back onto the linear track, whereupon their orientations will again be determined by the sensor as to whether they should be transferred by the turret handler to the test station(s) for testing.
A plan view of each electronic device generally defines a rectangular shape, wherein two opposing edges are longer than another two opposing edges. When an electronic device is in the desired orientation and is picked up by the respective pick heads of the turret handler, one of the shorter edges of the electronic devices points directly towards the turret handler. In other words, the long edges of the electronic device are arranged orthogonally with respect to a circumferential path along which the turret handler rotates. Similarly, each pick head comprises a vacuum suction cavity that is also generally of a rectangular shape. However, the longer edges of the vacuum suction cavity do not correspond with the longer edges of the electronic device when the electronic device is picked up. The same applies to the shorter edges of the vacuum suction cavity. In other words, the vacuum suction cavity of each pick head is typically offset by an angle of 90 degrees with respect to each electronic device when the electronic device is picked up. Accordingly, the actual pick-up force applied on the electronic devices for the purpose of holding the electronic devices is reduced and this increases the risk of the electronic devices being dropped during transfer by the pick heads, thereby affecting the operational throughput.